How does the sound of Buddha-recollection that spontaneously arises in the mind come into being? Who is recollecting the Buddha?

The recollection of the Buddha's name that arises involuntarily is initiated by the manas; it is the manas that is reciting the Buddha's name. At first, the mind consciousness cannot perceive it, and once it becomes aware of it, it cannot control it and has no choice but to follow along and listen to the sound of the Buddha's name. Being conscious is the mind consciousness's own awareness; being involuntary is not the mind consciousness's own awareness, but the awareness of the manas, the activity of the manas. This kind of buddha-recollection samādhi is a state of meditative concentration, and this concentration is relatively firm. Relying on this samādhi state, if one then engages in contemplative practice (vipaśyanā-caryā) of the four foundations of mindfulness, the mind is also pure, and contemplative practice becomes easy.

When the sound of reciting the Buddha's name arises involuntarily, continuing unbroken and lingering in the mind and the brain, this is buddha-recollection samādhi. All kinds of samādhi arise from the manas. Why can the manas give rise to samādhi? For those whose buddha-recollection practice is not yet mature, buddha-recollection samādhi will not appear; for those whose contemplative practice in various respects is insufficient, samādhi states will not appear either. What is meant by mature practice is that, through long-term persistence in one kind of cultivation, the manas has been successfully infused and influenced; once the manas has been thoroughly infused and shaped, it will automatically and spontaneously recite the Buddha's name and engage in contemplative practice, and then all kinds of samādhi will appear. The arising of various samādhi states is not decided by the mind consciousness and is not controlled by it; the mind consciousness can only passively accept them, passively merging into the samādhi state to experience the samādhi and the feelings of body and mind.